The only one ive heard of is the one Brian gave to roger that he kept in his draw for months before falling in love with the song. I very much doubt that will see the light of day.
^^^^
wouldn't call that demo so far, as it is some kind of piano-playalong brian did on the epk of 'queen rocks' to show how the song is structured. you may call it some kind of post-humous demo perhaps :-D
quite uninteresting stuff, though.